1. Field of the Invention
The invention concerns polymerizable compositions that can be stored in a single container.
2. Description of the Related Art
U.S. Pat. No. 2,982,396 (Shihadeh) describes a single-package composition made from two reactive materials that polymerize when mixed. The composition can be stored in a single container. The reactive materials are separated by a "substantially inert and impermeable barrier ... adapted to resist the diffusion of either reactive component into the other for relatively long periods while permitting the entire contents of the one-package system including the barrier to be stirred into a substantially homogeneous and compatible mixture" (col. 1, lines 58-64). The barrier layer can be a liquid having a viscosity and density intermediate between those of the two polymerizable materials, or can be thixotropic or a gel, or can be a low-melting solid when the reaction between the two polymerizable materials is sufficiently exothermic to melt the solid barrier. Shihadeh's compositions are apparently designed for one-time use. In other words, they are not said to be useful for incremental (i.e., partial or repetitive) dispensing from the container.
Belgian Pat. No. 646,446 (patented Apr. 10, 1964) also concerns a container in which two or more reactive ingredients are separated by a barrier material that is said to be compatible with the reactive ingredients but neither reacts wtih them separately nor significantly diminishes the properties of the final product. The contents can either be mixed in the container before being extruded, or the container can be fitted with an extrusion nozzle containing a mixing element that mixes the materials when they are extruded. The Belgian patent says nothing about incremental dispensing and intervening storage of portions of the contents of the container.
Much of what is stated in the Belgian patent is repeated in U.K. Pat. Specification Nos. 1,065,560 and 1,072,272 and U.S. Pat. Nos. 3,462,008 (Tibbs '008) and 3,519,250 (Tibbs '250). None of these latter references suggests the incremental dispensing of less than the entire contents of the container at one time.